Chevron shaped article and a sandwich structure therefrom

ABSTRACT

1. A STRUCTURAL ELEMENT COMPRISING A SANDWICH OF TWO COVER SHEETS AND AN INTERPOSED CORE SHEET INTEGRALLY SECURED WITH THE COVER SHEETS, SAID CORE SHEET BEING CORRUGATED WITH THE CORRUGATIONS EXTENDING IN ZIG-ZAG PARALLEL ROWS AND EACH CORRUGATION HAVING A CREST RIDGE SECURED TO ONE COVER SHEET AND A VALLEY RIDGE SECURED TO THE OTHER COVER SHEET, SAID RIDGES TERMINATING IN A PEAKED EDGE SO THAT THE CORE SHEET CAN BE FORMED BY FOLDING FROM A FLAT SHEET WITHOUT STRETCHING THE MATERIAL, AND SAID CORRUGATIONS HAVING INCLINED PLANER SIDE WALLS BETWEEN THE CREST AND VALLEY RIDGES.

Oct. 17, 1972 v uc &698379 CHEVRON SHAPED ARTICLE AND A SANDWICHRRRRRRRRRRRRRRRR OM I&

/NVENTOR U//[N l /CTOR GEWSS Y W Oct. 1 7, 1972 v. G. LUCIEN 5 3 CHEVRONSHAPED ARTICLE AND A SANDWICH v STRUCTURE THEREFROM Filed June 9, 1955ll Sheets-Sheet 2 3 4 2 02 de d z ,3 a m s f e 3 Q 7 u? a a u( U of c nl71 a' /IVI/E/V TOR LHC/[N /TOR &TW/55 7 M dz ATTORNEYS Oct. 17, 1972 v.G. LUCIEN CHEVRON SHAPED ARTICLE AND A SANDWICH STRUCTURE THEREFROM llSheets-Sheet 5 Filed June 9, 1955 /YVEVTR U/C/[IV V/TOP & w/55 /M' ATTORNEYS' Oct. 17, 1972 v. G. LUCIEN 3,698,879

CHEVRON SHAPED ARTICLE AND A SANDWICH STRUCTURE THEREFROM Filed June 9,1955 ll Sheets-Sheet 4.

IN VEN TO R LHC/[N V/CTOR GEW/SS 5/ %iz-WM ATTORNEY&

Oct. 17, 1972 v LUCIEN 3,698,879

CHEVRON SHAPED ARTICLE AND A SANDWICH STRUCTURE THEREFROM Filed June 9,1955 ll Sheets-Sheet 5 /NVENTOR LU/EN V/CTR GEWSS BY M y Zi A T TORNE vsOct. 17, 1972 v. G. LUCIEN 3,698,879

CHEVRON SHAPED ARTICLE AND A SANDWICH STRUCTURE THEREFROM Filed June 9,1955 ll Sheets-Sheet 6 NVENTOR H z LHC/[N wow/e GEW/SS A T RNEVS l g k1972 v. G. LUCIEN 3,698,879

CHEVRON SHAPED ARTICLE AND A SANDWICH STRUCTURE THEREFROM Filed June 9,1955 ll Sheets-Sheet '7 /NVE/VTOR LHC/EN V/CTOR GEW/SS V &jam/(fli:

ATTORNEYS Oct. 17, 41972 v, e. LUClEN CHEVRON SHAPED ARTICLE AND ASANDWICH STRUCTURE THEREFROM ll Sheets-Sheet 8 Filed June 9, 1955l/VVENTOR [UC/[N V/CTOR GEWSS :By KM ATTORNEYS.

Luj L-4 Oct. 17, 1972 v. G. LUCIEN 3 CHEVRON SHAPED ARTICLE AND ASANDWICH STRUCTURE THEREFROM Filed June 9, 1955 ll Sheets-Sheet 9 /NVE/VTOR LHC/[N V/CTOR GW/SS 7,37 /M ATTORNEYS Oct. 17, 1972 v. G. LUCIENCHEVRON SHAPED ARTICLE AND A SANDWICH STRUCTURE THEREFROM llSheets-Sheet 10 Filed June 9, l955 m w m w Luc/[N vcmR czwss A TTOEWEYJ`y m/A n fa/ M Oct. 17, 1972 v uc 3,698,879

CHEVRON SHAPED ARTICLE AND A SANDWICH STRUCTURE THEREFROM Filed June 9,1955 11 Sheets-Sheet l EES h ...llllllm ATTORNEYS United States Patent OInt. c. B2b 15/00 U.S. CI. 29-191 24 Claims ABSTRACT OF THE DISCLOSUREThe invention disclosed pertains a shape material which in general issheet or plate like in form. It consists of a general chevron structureto be used structurally and also for various articles of manufacture. Itpertains to a method of making which embraces forming various portionsof the chevron shape by bending. It likewise includes a machine forforming the particular material.

Building and the like materials are already known which appear in theshape of recessed, corrugated or the like plates. For a predeterminedthickness, such building materials have a generally reduced weighttogether with a large superficial area. These common basic propertiesare however generally not associated with certain further advantageousproperties which would increase their fields of use and lead to morewidely spread applications.

In particular, it would be of advantage with a view to answering morespecifically the requirements of numerous applications, for suchbuilding materials to be provided with larger, more numerous or moreuniformly distributed elementary bearing surfaces while said surfacesmight be deformable or expansible to a very large extent in two mutuallyorthogonal directions.

It is also of interest in the case of certain particular applicationsfor such materials to be produced not only in the shape of plates of apractically uniform thickness bounded by parallel surfaces, as isgenerally the case with recessed or corrugated structures of a knowntype, but more generally speaking of any suitable shapes defined bybounding surfaces also of any desired type, whether concave or convex oralternatingly convex and concave said surfaces being possibly diferentfrom generally plane surfaces.

It would also be of considerable interest to provide for the productionof such materials with any substance, while having in all cases aresistance to crushing which is proportionally very high, such materialsremaining however of a low cost price.

My invention has for its object to provide a novel article ofmanufacture constituted of a material the outer surfaces of which areprovided with recesses and projections arranged alternatingly inaccordance with a predetermined geometric law and which has been foundas remarkably favorable to the obtention of the above referred todesired results although its advantages are by no means limited thereto.My invention includes also various methods and arrangements for theproduction 3,698,879 Patented Oct. 17, 1972 ice of such novel materialstogether with numerous applications of the latter.

My improved material may be defined in its most general form as a solidhaving very small thickness, comprised between enclosing surfacestangent to its outer surfaces along ridge lines broken at differentpoints when changing direction, the ridge lines on one given surfacebeing connected with the adjacent ridge lines on the same surface whensuch adjacent ridge lines are present and with the immediately followingor preceding ridge lines on the other surface when such adjacent ridgelines are not present on the same surface, through flanks constituted byelementary ruled surfaces of any type having a single curvature, the sumof the angles formed by the sides of said elementary surfaces leading toany points of each of the ridge lines being always equal to 360.

The solid structure of my invention corresponding to the abovedefinition are generally provided with a plurality of series of more orless uniform zigzag grooves, more or less simular to V-shaped lines orchevrons facing alternate directions. For this reason, I will designatethem hereinafter by the expression chevron structures.

My invention covers also all the chevron structures of any general shapeand thickness of which at least one surface has a configurationidentical with that of one of the solid structures executed inaccordance with the above definition and it also covers any structurederived directly therefrom when the identity in shape s obvious in ageneral manner with slight differences in detail for reasons which willappear hereinafter.

Further features of my invention together with its main advantages andvarious manners of executing it will appear readily from the reading ofthe following specification, reference being made to the accompanyingdrawings given by way of exemplification and by no means in a limitingsense, in said drawings:

FIG. 1 is a perspective view of the outer configuration of a solidstructure the elements of which correspond to the general definition ofmy invention.

FIG. 2 shows the same structure when developed on a plane.

FIG. 3 shows a chevron structure including exclusively equalparallelograms arranged symmetrically two by two.

FIG. 4 shows the structure of FIG. 3 developed on a plane.

FIG. 5 illustrates a chevron structure the ridges of which have anundulating shape.

FIG. 6 illustrates a solid structure the elementary surfaces of whichinclude exclusively triangles of two different shapes and furthertriangles symmetrical with reference to the latter.

FIG. 7 shows the solid structure of FIG. 5 developed on a plane.

FIG. 8 shows a structure similar to that of FIG. 5, but in which certainundulating ridges have had their positions reversed.

FIG. 9 is a perspective view of a portion of a chevron structure similarto that shown in FIG. 3 as it appears during the progressive formationof its Component elements.

FIGS. 10, 11, 12 and 13 are diagrammatic views of successive steps of amethod for the gradual progressive embossng or folding of the structurewhich may be re- 3 sorted to for the production of a chevron structureof the type illustrated in FIG. 9 with progressive increase of chevronpitch.

FIGS. 14 and 15 are diagrammatic plan and elevational views of differentparts of the machine adapted to define the operative movements to beperformed by a machine working in accordance with the first method byengagement between rigid jaws illustrated in FIGS. to 13.

FIG. 16 is a diagrammatic side elevational View, partly sectional, of amachine adapted to execute the chevron folds in accordance with a secondmethod.

FIG. 17 is a partial plan view corresponding to FIG. 16.

FIGS. 18 to 24 are partial diagrammatc cross-sectional viewsillustrating the positions of some of the chief components of themachine according to FIGS. 16 to 17 during an operative folding cycle.

FIG. 25 is a perspective view of a chevron structure of a particulartype adapted to be obtained through the operation of a machine similarto that illustrated in FIGS. 16 and 17 according to the second method.

In FIG. 1 illustrating a chevron structure corresponding to the generaldefiniton of the invention described hereinabove, one of the surfaces ofthe solid structure carries a plurality of independent ridge lines a, b,c h, a 17 c g together with a bundle of ridge lines including twoadjacent sections a b c g and c d which latter opens in its turn at d toform two further ridge lines d g h k and d e f i The other surface ofthe structure carries the ridge line shown in inner lines d I, m p; anda bundle of ridge lines p g diverging at the point g into two sections gq r a and g q r v a The two surfaces enclosing the structure and the twosurfaces of the latter are thus provided in this particular case withcommon points a g and d constituted by the meeting points between ridgelines on the two surfaces.

The different elementary ruled surfaces filling in an uninterruptedmanner the fianks or spaces defined between the ridges of the chevronstructure mate to a certain extent the shape of each of the linesbounding them since their common rectilinear generating line follows thedifferent outlines of the elementary surfaces while forming a certainangle therewith. The fianks constituted by sequences of elementarysurfaces of the chevron structure are generally provided with folds andbending lines at each abrupt modification in the direction or in thecurvature of the ridge line. All these breaks and bending lines formstraight elements since they form the intersection 'between adjacentruled surfaces.

Under such conditions, the bodies in space formed by the elementaryruled surfaces with a single curvature following each other along thefianks of the structure defined by the ridge lines are limited by threeor four lines of which two at least are straight and are formed by foldsor bending lines separating said elementary surfaces. These elementarysurfaces form thus 'fiat foursided members bounded by straight elements,meeting each other or parallel, of two successive ridge lines. Between astraight element of one of two successive ridge lines and a point of theother ridge line, said elementary surfaces form flat triangles. Betweenthe homothetic elements of two incurved or concave successive ridgelines, the four-sided figures are constituted by sections of a cylinder,of a frusto-cone, of an ellipsoid, of a paraboloid, etc. Between onecurved element of one ridge line and a point of the next ridge line,these elementary surfaces form three-sided portions of a cone or of anapproximately conical surface.

Each of the elementary surfaces comprised between two successive suchridge lines may be developed on a plane, since it is constitutedexclusively of ruled figures having three or four sides, which are flator incurved, are positioned endwise and are separated from one anotherby straight ridge lines which may be straightened out so that saidfigures are actually developable on a plane. Each of the fianks formedby the elementary surfaces along any ridge line assumes consequentlywhen flattened the shape of a succession of flattened three orfour-sided figures with straight or curvilinear sides separated by thefolds or bending lines defining them on the solid chevron structure.

When positioned side by side, all the edges adjacent the elementarysurfaces thus developed coincide as shown in FIG. 2. As a matter offact, each of the different ridge lines forming each both the edge ofone elementary surface and the corresponding edge of the adjacentelementary surface cannot, when spread in a common plane, provideanything else except the final developed surface referred to, since ithas been assumed by way of a definition that the different successiveangles defining the first edge are precisely the complement withreference to 360 of the corresponding angles of the same magnitudeforming the second edge.

It is important to remark at this point that the different points ofconvergence between the ridge lines and the folds or bending linesdefine in all cases at least four angles helonging to at least as manyseparate adjacent elementary surfaces.

The solids with very small thickness or the surfaces which form theobject of my invention as defined hereinabove, are consequently, inspite of their chevron structure which may apparently be very intricate,of a substantial simple structure since they are always developable on aplane. This property may be considered as inherent to the thick solidstructures forming also the object of my invention, at least inasmuch astheir deformability or malleability is sufiicient for them to providewhen flattened out in the thickness considered, a straightening of thebent and folded sections of the structure and of the ridge lines. Whendeveloped, the thick structure of such solids is that of a mere sheet ofa material retaining the original thickness with the allowance to bemade for a few deformations arising through imperfect straighteningOperations.

The above remarks show that any very thin chevron structure, or thethickness of which allows, taking into account the nature of thesubstance forming the structure, an accurate development on a plane, maybe flattened through a mere straightening of the warped surfaces, ridgesand folds. During the flattening out of the structure, the height of thelatter is gradually reduced at all points; as a counterpart, thestructure occupies a surface which increases at the same time in anuninterrupted manner both as to breadth and to length, said increasebeing however generally non-uniform.

The outer geometrical Outline of any chevron structure when flattenedout is thus defined by the joining outlines drawn on a plane at a scaleof 1/1 and in suitable sequence of the different elementary surfacesforming it; the compound outline thus obtained defines furthermorethroughout its extent the exact location of all the straight orcurvilinear folds which, when executed simultaneously with the suitabledegree of folding, allow re-forming the original structure.

From the preceding disclosure, it appears naturally that the basicmethod which allows forming a predetermined chevron structure whateverit may be is obvious. As a matter of fact, it is suflicient to draw on asheet of the substance to be used the different elementary surfacesforming the compound Outline of a predetermined structure, and then tofold the sheet in the desired directions along the lines thus drawn,said folds being gradually made more marked throughout the eXtent of thesheet. Since the chevron structures are to satisfy predeterminedrequirements of the applications to be considered, the shape of thedifferent elements thereof should be designed and executed in accordancewith said requirements. It is necessary to proceed through successiveempiric steps or else to rely on suitable mathematical calculations.

Finally the outlines obtained allows folding the sheet into the desiredstructural shape.

In practice any joining outline for the different three and four sidedelementary figures, having at least two straight sides opposed to eachother, i.e. triangles or four-sided members having curvilinear sides orotherwise, is generally adapted to be folded in the shape of a chevronstructure. It is however necessary for all the points of convergence ofthe ridge lines, of the folds or bending lines to form for the reasonsdisclosed hereinabove the ends of four independent lines at least.

The reproduction of an outline may then be executed through any suitablemeans such as a printing press, a press provided with a marking tool, orelse through photographic processes and the like.

Before proceeding with the chevron folding of a suitably outlinedstructure, it is necessary to select in any suitable manner, among thedifferent lines, those lines and bundles of lines wihch are adapted toform the ridges of the structures to be established, provided howeverthe selected lines include of necessity all the incurved lines since thefolds or bending lines cannot include such incurved lines and must inall cases be straight.

Generally speaking, the general outline thus resorted to should now becompleted. It is important to draw as a matter of fact, between thesuccessive ridge lines, folds or bending lines as required by thedefinition of the present invention and which might not be present insaid general outline.

During the folding into chevron shape of an outline of this type theparts of which may be widely different, it should be remembered that allthe elementary surfaces are shifted simultaneously out of the plane ofthe original sheet and that some of these elementary surfaces will risemore steeply than others. These particular surfaces in fact will movenearer the elementary surfaces facing them at a higher rate than others.There arrives consequently a moment at which during the formation of thedifferent folds throughout the extent of the structure which is beingexecuted, two predetermined surfaces, turning round their common sidealong which said surfaces engage each other before other surfaces, comethus into contact. The two planes forming said elementary surfaces, ortangent thereto if they are curvilinear, are then merged into oneanother.

At such particular points and only at such points, any increase in thefolding becomes impossible, whereas nothing similar occurs at the otherpoints of the structure. However, the interdependence between thedifferent surfaces considered prevents the chevron folding of theoutlined sheet from continuing any further. There is thus obtained atthis moment a locking of the structure.

The chevron folding of somewhat intricately outlined sheets is alwayslimited in its progression through such a locking. This is moreover thecase of all outlined sheets even when comparatively simple but wherein acertain lack of symmetry prevents a corresponding progression in thefolding of all the elementary figures drawn thereon.

Among the simpler outlines which may generally be folded into chevronshaving joining folds throughout their extent, I may mention those whichare constituted of a very small number of different figures repeateduniformly such as parallelograms, trapeziums, triangles and the like.These outlines lead to the obtention of the structures which are theeasiest to be obtained through mechanical means and they are also thosewhich may be used more generally.

The most characteristic particular structure of this type (FIG. 3) isthat which is constituted exclusively by series of two symmetricalsimilar parallelograms. The developed -flat outline leading to theexecution of such a structure (FIG. 4) produces flanks or parallel rowsof identical elementary surfaces separated by equidistant broken ridgelines bounding similar elementary surfaces and forming with one anotherequal angles; such a structure which, by reason of its symmetricalarrangement, is foldable into chevrons with joining folds, present atall stages of its gradual formation two outer flat parallel enclosingsurfaces. The distance between said two enclosing surfaces which passesduring said formation from the plane of the original outline to theheight of the parallelogram extending between the ridge elements dependsobviously at every moment on the extent of folding of the structure.

When the parallelograms forming such a structure are equal only for eachof the successive rows, the preceding disclosure is true only betweentwo successive rows. In this case, the outer enclosing surfaces includeas many successive parallel planes as there are different heights forthe parallelograms (FIG. 25).

If in the description, I resort no longer to a single type ofparallelogram, but to different parallelograms having equal acute anglesand the same height but different breadths, said parallelograms beingassociated in joining relationship with symmetrical parallelograms, thestructure formed shows the same characteristics as to parallelism as theprecedingly described structure. Only its outer appearance shows thelack of equality between its component members.

When, in addition to dilferences as in breadth, the acute angles arealso different, nothing is altered in the general features of thestructure. However, the irregularities in the angles lead to a lockingduring the folding procedure so that the structure cannot be folded intochevrons with joining folds.

When, throughout the length of each of the elementary surfaces of astructure, the successive `parallelograms have the same height and thesame breadth while their acute angles diifer from one parallelogram toanother, said angle increasing first and then decreasing and thisrepeatedly in a continuous manner to either side of each of the ridgelines, the different parallel broken ridge lines which are all similarto one another have a generally sinuous shape.

A limiting case is reached when the parallelograms are so narrow thattheir breadth becomes negligible. This leads to a family of structuresof an undulating type as shown in FIG. 5, which are remarkable throughthe fact that the folds in the flanks connecting together the apices ofthe ridge lines disappear and are replaced by bending lines definingtheir changes in curvature. The two outer surfaces of such structuresare plane and parallel when the ridge lines are equidistant while theyare stepped in echelon in the general case. The bending lines of theflanks define the locking points of such structures.

In the case of such an undulating structure, as is the case With all ofthe structures of the present invention, the ruled elementary surfacesforming the walls of the protrusions and recesses of the sheet join oneanother along lines having points at which they change direction and ateach of which points border lines of at least four of said elementarysurfaces converge, the sum of the angles formed on said surfaces betweensaid border lines at each of said points being equal to 3 60. In thestructures having fiat surfaces, the presence of the four convergingborder lines is readily apparent. In the undulating structures, thisfeature is also clearly present, the border lines of the elementarysurfaces which converge at each of the points on the undulating ridgelines being constituted by the generating lines of each pair of surfacesmerging to form a ridge line, together with the halftangent line of eachside of the point of tangency of a line drawn tangent to the ridge lineat each of said points.

By associating in the flat outline triangles of two different .butsimilar types and their symmetrical counterparts, it is possible toconstitute chevron structures which are somewhat more intricate thanthose described hereinabove while their applications are quiteremarkable (see FIGS. 6 and 7).

The substitution for such folded ridge lines in such outlines, ofundulating lines allows obtaining structures which present withreference to those which have been heretofore defined difierencessimilar to those mentioned hereinabove as far as parallelograms areconcerned.

Within the limited scope of the present disclosure, it is impossible todescribe all the groups of structures falling within the generaldefinition set forth hereinabove and claimed in the accompanying claims.It should be mentioned however that the ridge lines are not of necessityparallel with one another. In the case where these lines converge thestructures are circular. Their boundary surfaces are then constituted byconical surfaces which are simple or multiple according as to whetherthe spacings between the ridge lines are equal or otherwise.

Whatever may be the configuration of a predetermined structure, it isalways possible to substitute for one or more ridge lines, one or morebundles of lines, provided however one remains within the scope of theabove referred to definition. As a matter of fact, it is sufficient toturn inwardly, partly or totally, a number of the convex sections of theridge lines formed by such a structure by proceeding with a depressionof each of them between the elementry boundary surfaces so as totransform said sections into as many concave lines bounding twotransformed surfaces constituted by the material of the formerelementary surfaces whereby two further intermediate convex ridge linesare obtained. Each further ridge bundle thus produced increases thenumber of flanks constituted by lateral elementary surfaces, whilereducing to a certain extent at the points considered, the distancebetween the enclosing surfaces.

By combining all or part of the means falling within the scope of myinvention as claimed in the accompanying claims, which means have alsobeen defined hereinabove, it is apparent that while resorting only toone very simple type of embodiment of chevron structures such as thatwhich allows producing undulating configurations, it is always possibleto produce a solid structure adapted to fill with the desired accuracy apredetermined space even of a complex nature bounded for instancebetween any two ruled surfaces or between any two incurved surfaces(FIG. 8). It is suicient to resort, to this end, when executing thedesired Outline of a flat sheet, to the expedient provided by themodifications in the distances between the fianks, the subdivision ofthe ridge lines into bundles and possibly the incorporation of suitablefolds and bending lines, so as to modify as required any simplestructure the elementary surfaces of which are flat and parallel whilethe detail of the structure is brought to the desired final shape. Inthe example illustrated in FIG. 8, which illustrates a chevronstructure, similar to that illustrated in FIG. but with modification, itis apparent that the convex ridge lines A Az have been depressed over apart of their length which leads to the formation of concave ridge linesB Bg comprised respectively between two further convex ridge lines asshown at A' A" and A' A" which leads to modifications in the distancebetween the surfaces enclosing the two sides of the structure.

All the chevron structure which it is possible to produce, whatever maybe their design, whether simple or otherwise are essentially deformable,since the folds provide their own yieldingness for cooperation with thedeformability or malleability inherent to the sheet material formingsaid structure. For any structure, the importance of the possible localdeformations varies however to a considerable extent, in accordance withthe areas to be considered, as provided by the number, the importanceand the arrangement of the lines and elementary surfaces to beconsidered in said area; the structure which have the simplestconstitution and which are the most homogeneous are those wherein thepossibilities of de formation are distributed in the most uniformmanner.

8 Such structures may very readily mate with the surfaces on which theyare to rest.

In all cases, it is an easy matter to increase to a very large extentthe yielding or resilient character of any predetermined structure,solely by closing its folds as much as possible; the structures whichare liable to be locked such as the corrugated or undulating structuresfor instance, lose naturally much of their original yielding characteras the chevron folding approaches the locking oint.

P Chevron structures according to the present invention oer a very highresstance to the loads transmitted, locally or otherwise, between thetwo large enclosing surfaces of the structure.

The fianks or series of elementary surfaces bounded by the ridges are asa matter of fact braced with reference to one another in anuninterrupted manner so as to balance and to absorb the slidingComponents acting perpendicularly to the stresses applied to thestructure. The numerous olds and bending lines extending across saidflanks form between successive ridge lines, angularly shaped orcurvilinear stifening members preventing any buckling throughout theirextent.

The fianks behave thus as so many rigid stays securely anchored betweenthe enclosing surfaces. Simple and symmetrical structures which areenclosed between two flat parallel surfaces are those which provide thehighest resistance to crushing loads, chiey when their flanks areundulating, because they are remarkably homogenous and any desirednumber of folds may be closed along sloping planes as near to thedirection of the stresses to be resisted as may be considered necessary.

I have thus defined the more salient properties of chevron structures.These explanations provide understanding of how the different substancesused for forming such structures require, during the chevron foldingoperation, novel properties which are generally associated with thosenormally shown by them at the start. These supplementary properties arethe following in the case of a chevron structure with close folds:

A large superfical extent for the amount of substance housed with in areduced enclosing Volume.

A very large elasticity in the hearing of all the ridges of thestructure throughout the extent of the enclosing surfaces.

A high resstance against crushing since said resstance is that of theactual solid material when the folds join one another.

A practically unvarying height between the two bearing surfaces in spiteof the modifications which may occur simultaneously throughout thebreadth and the length of the structure.

Or in other words:

A large range of possible modifications in breadth and in height for apractically unvariable height between the two outer enclosing surfaces,

A complete lack of response to the action of expansion produced by heatin the direction of the length and of the breadth of the two outersurfaces.

Each of the properties of the chevron structures defined hereinaboveloses its value to a certain extent when the folds open more widely withreference to one another. In contradistinction, when said folds arespread out or released, a novel property which is a light weight, isobtained and develops. The specific weight of a structure which is, whenthe folds lie in joining relationship, exactly that of the materialforming them decreases proportionally in an obvious manner when theVolume increases. This specific weight is, for its lowest value, equalto an always very low figure when the structure reaches its maximumVolume. Beyond this predetermined position of the opening of the folds,the structure loses some of its Volume and the value of the specificweight increases. Finally, when the sheet is spread out or developedagain over a flat surface, the specific weight is again that of theoriginal solid material.

The most favorable compromise to be found between the first mentionedproperties and the last i.e. a reduced weight, taking also into accountthe cost price of the whole arrangement, allows defining for apredetermined type of substance the more or less considerable opening ofthe folds to be provided so as to satisfy fully the requirements of theapplications to be considered.

The principal applications of the chevron structures according to thepresent invention are chiefly and according to the substances used, asfollows: paper, fabric, felt, filtering metal gauzes, porous substancessuch as ceramic ware, when provided with chevrons having joining foldsor at least close folds are adapted to produce filtering layers andfiltering elements of any szes, as required for the purfication of allliquids and gases and in particular for removing the the dust from air.

Metal sheets such as steel sheets when formed with chevrons having loosefolds, allow producing sheets which are more yielding than corrugatedmetal sheets and which may be used as such for covering roofs andcoating the walls and floors of sheds, houses and the like, or else theymay be worked into the shape of central heating radiators, heatexchangers and pressure transmitters, thermostatic casing or compressordiaphragms.

These chevron-shaped elements which may be made of a substance differentfrom metal such as paper, fabric, plastic material, glass, plaster ofParis, cement, agglomerated material or the like, are also applicablefor the ornamental coating of walls, cellings etc. in halls, theatersand the like or even =in the rooms of private residences.

The manufacture of paper, cardboard, plastic material and the like inchevron shape adapted for those uses for which corrugated paper andcardboard are used for packing and the like purposes; even in the caseof considerable thickness, forms one of the most interestingapplications of the invention since the resstance to crushing of saidmaterial when so formed in chevron structure is, for an equal Weight ofmaterial, several times higher than that of the conventional materialsprovided with a mere corrugation.

A further very important application is that which relates to theexecution of the network elements as resorted to for the so-calledsandwich material provided with recesses or cells within its body.Sandwich materials are well known in the art and essentially comprisespaced opposed cover sheets or skins having interposed between them acore sheet which is bonded to the cover sheets to form an integralstructure. Such structure is formed by bonding the crest ridges of thechevron cores of the present application to one of the cover sheets orskins and by bonding the valley ridges of such cores to the spaced,opposed cover sheet or skin. Viewing the core material of FIG. 3 as partof a sandwich structure, for example, the ultimate structure wouldcontain a core sheet having corrugations extendingin Zig-Zag parallelrows from one side to the opposite side of the sandwich structure witheach corrugation having crest ridges Secured to one cover sheet andValley ridges secured to the other cover sheet, said ridges terminatingin peaked edges and said corrugations having inclined planar side wallsbetween the crest and Valley ridges. Quite obviously, the corrugationsof such a sandwich structure will necessarily define flow passagesthrough the structure as fabricated.

Chevron structures of the foregoing type forming plates of any desiredsubstance or preferably of any combination of substances including,according to the case, paper, plastic material, agglomerated material,glass, cement, plaster of Paris, metal sheet and the like, etc., show,when compared with similar conventional materials, and in addition to alighter weight and a more considerable rigidity in shape, much moremarked insulating properties with respect to sound vibrations and heat(through radiation 10 and conductivity) which are much more considerableand are associated with an extremely low cost price.

In the building industry, sandwich chevron-plates may serve forexecuting partitions, ceilings, roofs, walls, prefabricated panels forhouses, structural blocks and the like.

In the case of joiner s work, the improved chevron structures, chieflysandwich plates may serve for executing thick panels, hollow elementsfor pieces of furniture, light and rigid doors, imitation thick plywoodof any type.

The partitions and floors in ships, railway Compartments, telephonebooths, aircraft cockpits, are advantageously executed with such chevronplates whether fiat or incurved.

The filling of the wings, fins and incurved connecting elements foraircrafts and certain light buildings may also be executed easily and ata low cost price through the use of my chevron structures.

The chevron shaping of yielding substances such as rubber and plasticmaterial in a solid or cellular or spongy state produces yielding andresisting elements and blocks which allow forming cushions, seats,mattresses, yielding carpets, antivibrating supports for machines,yielding diaphragms of any type and deformable fluidtight casings.

The means which are the most suitable for ensuring the manufacture ofmaterial shaped in accordance with my invention are selected, takinginto account the configuration of the structures to be executed and thenature of the substance forming them and also the state in which thesubstance is used.

In the case of chevron structures of a uniform thickness which are to beexecuted with a substance having a sufficient deformability ormalleability and formed in sheets having the desired thickness, it hasbeen mentioned already that in accordance with a first method ofproduction the structure is executed gradually progressively by hand inconformity with a previously drawn line, this operation being performedthroughout the extent of the sheet, care being taken to fold the sheetin the desired alternating directions. This method is applicable to theexecution of all types of chevron structures, whatever may be thecomplexity of their configuration, provided however that the substanceselected may be brought first into the shape of sheets which aredeformable or malleable when assuming the required thickness, saidsubstance being then used in said sheet form.

There is available a second method, in the case of substances which aremore easily obtainable in other shapes or which are not malleable insubstantial thicknesses, such as plaster of Paris, cement, plasticmaterial, agglomerated material, cerarnic ware, cellulosic substances,metals and the like, for which it is often of advantage to proceedthrough casting or molding at a suitable temperature and under asuitable pressure between the two halves of a mold. Certan substancessuch as rubber are necessarily treated in accordance with this method.

It should be remarked that the different Components of said structuresmay be molded in a very eflicient manner because, considered as a whole,taking no account of certain details of intricate structures, theraising of said structure is obtained perfectly by reason of the obliqueposition of the flanks extending along the ridge lines.

The mold Components should be executed by means of substances suitingthe molding methods employed, i.e. generally plaster of Paris in thecase of the molding of plaster of Paris, cement, pottery slip, etc., orelse metal when molding plastic material and rubber or again wire net orthe like for washers containing cellulosic fibres to be laid in positionor sand for molten metals, etc.

The execution of mold elements which normally would be intricate andcostly by reason of the difficulties of machining arising through theintricacy and interengaging configuration of the flanks along the ridgelines, may in practice be executed very simply in most cases, since itis 1 1 sufficient to proceed, with a view to obtaining them accurately,by molding structures forming patterns, which have been previously madeby hand in the desired shape by resorting for instance to strong paperor thin metal covered if required with varnsh or plastic material.

The various methods of casting or molding considered will allowproducing easily all chevron structures having two bounding surfacesremaining at equal distances from each other or otherwise, and alsomassive chevron structures of any type bounded by one or more boundingsurfaces of any shape whatever.

Chevron structures executed through molding in the manner disclosedhereinafter are in conformity with the structures defined hereinabovesince the molding reproduces strictly all the details in shape of thedevelopable structures forming the patterns.

However, I may resort to the fact that the molds thus produced may bereadily modified as concerns the details of their shapes with a view togiving the solid structures formed certain further convenient or usefulfeatures or properties. Thus the thickness of the material may be nolonger uniform but it may be reinforced at certain points, if requiredfor instance through the use of ribs fitted over the fianks so as togive the structure a greater local rigidity or a greater resistance. Theangles may be rounded and the ridges less sharp. In certain cases, itmay be desired to incorporate into the basic chevron structure hooking,positioning and the like elements without unduly widening thereby thescope of my invention as defined in the accompanying claims.

When providing for mass production of thin chevron structures of asimple configuration and when it is possible to resort to this end todeformable or malleable substances which may be obtained chiefly in theshape of sheets, it is of advantage to resort to one of the followingmechanical production methods:

(a) Folding into chevron shape through the intrusion of the differentsurface elements forming the successive flanks along the ridge linesdrawn on a continuous plane sheet between two jaw systems adapted toassume a receding motion which may include progressive increase ofchevron pitch.

(b) Forming into chevron shape by reversng in one flank out of two thelongitudinal folds of a sheet fed in a continuous manner.

The first-mentioned method of the mechanical folding into chevronsthrough engagement of the successive surface elements of a continuoussheet between two jaws, resorts to the possible local deformation of anychevron structure of a reduced thickness and more particularly to thepossibility of drawing out superficially such a structure across theflanks for instance. As a limit, it should be remarked that such astructure held in its original shape at one of its ends, may becompletely stretched or drawn out or developed on a flat surface at itsother end.

FIG. 9 shows a chevron structure thus drawn out according to the firstmethod and comprising exclusively a predetermined parallelogram shapeand a symmetrical parallelogram. This figure shows how it is possibleconversely to pass gradually, imperceptibly and continuously from a flatshape to the final chevron shape.

The sheet is flat in the area a. In the area b, it is provided with twolines of folds to be made later on to form the ridges. In the area c,the first folding or pleating is initiated. In the area d, the pleatingis more marked and this continues gradually progressively in the arease, f, g. etc. up to l which defines the last groove beyond which theformation of the chevrons in the area m is submitted to its maximumfinal shaping.

At a, the sheet is flat; starting from c, it is pleated and defines twolimit surfaces C H K B and D M K B which are oblique with reference toeach other and are located to either side of the original plane of thesheet forming the structure. In the area m and beyond the same, thesurfaces F N M D and E G H C enclosing the i for a sheet which istheoretically of zero thickness, the

breadth Q Would be also equal to zero.

A machine for producing a chevron structure in accordance with the firstmethod which has been described with reference to FIG. 9, is illustrateddiagrammatically in FI-GS. 10 to 15. Hn said machine, the sheet to bepleated or folded enters in the direction of the arrow F (FIG. 10)between the two cooperating oblique embossing jaw bodies 1 and 2provided with as many movable dies as there are groups of say fouradjacert parallelograms. Dies such as 3 and 4 are fitted together ineach embossing plane in rows for each groove and also in longitudinalalignment. These dies which are closely fitted in adjacent relationshipassume together the accurate shape to be given to the sheet during thefolding step already described with reference to FIG. 92

This system of two embosisng jaws is supplemented on the rear i.e. onthe side feeding the paper, by the incorporation of two bars 5 and 6adapted to mark the folds in the flat sheet, which may be obtainedthrough annealing for certain substances such as metals; behind thesebars are two independent clamping bars 7 and 8 while there is providedto the front of the machine and facing the finished plate a bolt 9adapted to engage one of the grooves of the chevron structure as itpasses out of the shaping means just described.

At the beginning of the shaping cycle (FIG. 10), the two embossingsurfaces of the machine are in complete oontacting relationship, thedifferent dies being closed towards the front and being fitted exactlyinside one another taking into account the thickness of the sheet heldbetween them. The sheet assumes thus mechanically at this moment theshape given to it by the dies i.e. the optimum shape for gradual folding(FIG. 9). However, in practice each of the folds has been submitted atthe end of the preceding clamping stroke to an elastic defor matiorwhich is not negligible and which produces a substantial generalrelaxation at the moment of the release of the dies.

Taking into account the preceding disclosure, the following movementsare obtained (FIG. 11) starting from the position illustrated in 'FIG.10.

The rear bars 7 and 8 clamping the sheet are fastened over theunimpressed section of the sheet and the bolt 9 sinks into a finishedgroove.

The embossing surfaces 1 and 2 move apart gradually and the same is thecase for the marking bars 5 and 6; during this opening movement the diesand the bars 5 and 6 recede laterally (FIG. ll) while the clamping bars7 and 8 move rearwardly by an amount at least equal to that by which thesheet expands.

At the end of the stroke (FIG. 12), the embossing surfaces 1 and 2 openapart to a maximum. Since each row of dies has moved rearwardly by onegroove interval, it is then located exactly above the group ofparallelograms preceding that formed by its precedingly. The markingbars 5 and 6 are in their turn positioned accurately above the nextsection of sheet to be engaged between the jaws.

Without the dies or marking bars moving any more, the embossing jaws 1and 2 move towards each other to a suificient extent for the tips of thedies to just come into contact with the corresponding hollows of thesheet. In contradistinction, the marking bars 5 and 6 have becomeoperative during this stage and mark in the sheet the lines defining thefuture folds. The position reached is that illustrated in FIG. 13 whenthe two clamping bars 7 and 8 are released and the bolt 9 has risen.

The marking bars and 6 begin then their gradual forward movement andcarry along with them the unimpressed sheet. Their part consists cheflyin urging forwardly, through the free spaces left by the dies whichclose in the three directions of space with reference to each other, thesections of the sheet which are submitted to a gradual progressivefolding procedure. During this progression of the bars, each row of diesprogresses positively under the action of a lever system describedhereinafter at the desired speed and through the suitable distance, saidspeed and distance being more coniderable when the row of diesconsidered is nearer the rear end of the sheet. v

At the same time, the two fastening bars 7 and 8 which are always open,return into their foremost location. The system has thus returned intothe position llustrated in FIG. 10. During the cycle of Operations whichhas just been completed or described, a groove of the chevron structurehas been released and a further area of the sheet has entered the jaws.The cycle of operation may now be repeated.

It is important to remark that the above described machine exertspreferably no embossing or stamping or forming Stress. The embossingjaws 1 and 2 and the dies provided thereon form only inert molds betweenwhich the sheet to be shaped is introduced gradually and against whichit bears during the folding procedure. The useful drivng stresses isexerted solely by the marking bars 5 and 6 pushing in front of themthrough intrusion and in sequence the successive sheet areas which areto form further folds.

Of course, the lengths of the diferent rows of dies vary between thewhole breadth of the sheet at the rear and the breadth of the chevronstructure to the front.

FIGS. 14 and 15 are diagrammatic elevational and plan views of one ofthe numerous control means which may serve for controlling the abovedescribed movable parts. The two embossing jaw bodies 1 and 2 over whichthe dies such as 3 and 4 are adapted to move, are held in front of eachother and clamped together by means of a double set of guides andsprings 10, 11 and 12, 13 provided laterally. The two embossing surfacesmay be shifted away from each other by acting on two points on the sideof each of their front and rear ends through the agency of cams 14 and14' actuated by levers 15 and 16 and by pusher members 17 and 18controlled in their turn by master cams 19 and 20 fixedly attached tothe drivng shaft 21.

The dies such as 3 and 4 are adapted to move in parallelism with theplanes of the corresponding bodies 1 and 2 while the two marking bars 5and 6 follow in contradistinction the mean horizontal plane of thesheet. To this end, the frame carrying the two embossing jaws carrysuitable lateral slideways 2 2, 23, which guide the bars 5 and 6 andcarry them along with them through their ends, while leaving a certainfreedom for said bars in a vertical direction so that their clamping maybe provided slightly before the clamping of the embossing jaws.

The above description shows that each die should move in the threedirections of space during the time required for the progression of thebars 5 and 6. To this end, the dies are held in contact with the jawbodies 1 and 2, by longitudinal guiding rods or slideways, the axes ofwhich are projected in plan View as shown in FIG. 15 on lines such as24, 25 and 26, 27 in the case of the particular die 28, which is theonly one illustrated. The slideways such as 24, 25, are stationary withreference to the planes of the jaw bodies 1 and 2 while the rods such as26, 27, providing for the alignment of the rows of dies are movable. Thedies driven by said rods slide over the slideways along the jaw bodies&1 or 2.

The drivng of the rows of dies may be executed in various manners. Thesimplest is illustrated in BIG. 15 which is a half plan view of theembossing jaw 1. The bar 5 carrying at each end a rod 29 is connectedthrough a blade 30 with a lever 31 pivotally secured to the point 3211.Sirnilarly the end 32 of the rods 26 and 27 corresponding to each row ofdies is connected through a blade 33 with the same lever 31. Thus, allthe movements of the marking bar 5 are associated accurately withsimilar movements of different rods such as 26, 27 connecting the dies,but the speed and length of travel of the different parts is at anymoment proportional to the distances between the points at which theblades are pivotally secured to the lever 31 and the pivotal connection32' respectively. A similar arrangement is obviously provided also forthe embossing jaw body 2.

This satisfies the multiple cooperating conditions governng themovements imparted to the bars and dies as disclosed hereinabove. i

`In FIG. 14, there is shown a lever 34 which urges forwardly andwithdraws then rearwardly in alternation, the associated bars 5 and 6 soas to ensure equally the shifting of all the dies. It is actuated alsoby the master cam 35 mounted on the drivng shaft through the agency ofthe pusher member 36.

The clamping bars 7 and 8 which are to be tightened and also to beshifted longitudinally are carried by lateral slideways 37 and 38pivotally secured at 39' to each other. To either side of thearrangement, a cam 40 controlled also by a master cam 'keyed to thedrivng shaft 21, produces through cooperating pusher members the openingand the closing of said slideways 37 and 38. Two springs 41 and 42transrnt to said clamping bars 7 and 8 the required compressng Stress.The shifting of said bars is performed by means of a lateral lever 43which also receives its movement through a cam mounted on the drivngshaft 2 1.

Lastly, the pivoting bolt 9 at the front is controlled similarly on eachside by a lever and a rod driven similarly by a cam fixedly attached tothe drivng shaft 21.

The machine thus described is obviously disclosed only by way ofexemplification and the arrangements to be provided in each case dependobviously to a large extent on the type and characteristic properties ofthe substance forming the sheet to be worked. 'It may be of advantage inparticular to om't the clamping bars 7 and 8` and the bolt 9 F-IGS. 10to 13) and to make the rising movements of the different rows of diesindependent from one another.

The different rows of dies in such a machine of FIG. 14 according to thefirst method are thus not rigid with the embossing jaw bodies. When itis desired to progress by a one groove interval before the dies reengagefor a folding step, the rows of dies rise individually and in successionfrom the rear to the front while the other rows of dies continue holdingthe sheet which is being folded.

The chevron folding through reversal of longitudinal folds in one :flankout of two in accordance with the second method referred to hereinabove,requires mechan ical means adapted to locally turn round in successivetransverse sections the molds for a sheet of substance which has beenpreviously folded or corrugated in a longitudinal direction. A machineexecuting such a reversal method includes therefore in principle twowell defined separate sections. The first section is equpped with a rollof the substance as sold in trade; it includes the mechanisms requiredfor corrugating or folding the sheet which is to be providedcontinuously with chevrons in a longitudinal direction. The secondsection of the machine includes the mechanism which are to produce thedesired alternating transverse reversal of the folds of corrugation ofthe sheet.

FIGS. 16 and 17 show diagrammatically the main membars of such amachine. The sheet to be shaped 45 winds ofi the roll 44 and after acertain travel forms an abrupt bend at R and it then enters in flatformation inside a harrow arrangement 46-46' providing for its gradualprogressive folding.

The sheet, longitudinally corrugated and folded by the arrangement46-46', passes out of same at S where its 15 shape corresponds more orless accurately with that of either type of flank which it is desred toproduce for the chevron structure. This shape is more or less exactlythe reverse of the shape of the second type of flank. The breadth of thecorrugated sheet at S is consequently already that of the final chevronstructure to be obtained.

The folding arrangement includes two harrows 46 and 46' constituted eachby as many longitudinal blades as there should be folds or corrugationsin the sheet. The blades are arran-ged so as to converge and thus takeinto account the reduction in breadth imparted gradually progressivelyto the sheet.

The blades of the harrow 46 and also of the harrow 46' are arrarged at Rin a manner such as to leave between them exactly the interval requiredfor the passage therethrough of the sheet in flat formation. At S incontradistinction i.e. at the output end, said harrow blades interengageby an amount adapted to give the sheet the desred shape.

The convergence of the harrow blades constrains one to feed the sheet atR in arcuate formation. This is provided by the bending of said sheet atR. At this point R, the sheet turns round a tore shaped cylinder orconcavely grooved pulley 47 having as its axis xx'. Through thiscontrivance, the sheet unwinding in flat formation from the roll 44assumes a shape which is more and more incurved and which matchesfinally that of the cylinder having aXis x-x'. The sheet turns round thelatter through an angle approximating 90 and it assumes again betweenthe harrows 46 and 46' a plane shape, but this time between convergentsides.

In practice, the unwinding of the sheet from the roll 44 and therotation of the tore-shaped cylinder or pulley 47 should be controlledmechanically in a manner such that the sheet 45 may be subjected inre-gister with the axis x-x' to no substantial tractional stress.Similarly, the energy required for the shaping of the sheet between theharrows 46 and 46' cannot, by reason of the high value of the frictionbetween the sheet and the harrow blades, be derived from the tractionalstress exerted by the second section of the machine. It is thereforenecessary to mechanically actuate the harrows in the Vicinity of theoutput end S by communicating thereto a reciprocating movement towardsand away from an optimum point, the amplitude of said reciprocationbeing very small and its frequency high. It is possible to resort tothis end to a mechanical, electro-magnetic or the like vibrator,provided however the driving unit selected has a sufficient power.

The tore-shaped cylinder 47 'may be consttuted by a yielding shaftcarried at its ends in bearings. It may as well include a plurality ofcardan joints. Independent rollers carried by a stationary curvilinearshaft may also be suitable, provided they are rigidly interconnected forsynchronous rotation.

The shaped sheet arriving at the delivery point S engages then the gapbetween four transverse .movable bars 48-48' and 49-49', the mechanicaldesign and shape of which are such that when they are brought near eachother they fill up accurately four successive transverse recesses formedin the chevron structure during its being formed. The sheet firstengages the gap between the two first bars 48-48' forming cooperatingjaws. At the beginning of the operative cycle of the machine, said twobars engage each other tightly while holding fast between them a sheetarea adapted to form, further on, a flank of similar outline in thestructure along a given ridge line. A similar sheet area which wasprecedingly clamped between the bars 48 and 48' durim-g the precedingcycle is simultaneously held fast between the two bars 49 and 49', thedistance between the two sheet areas clamped between the two pairs ofbars being spaced by two fiank intervals.

The operation of the machine of FIGS. 16 and l7 provided with these fourbars is as follows:

The jaws 48, 48' begin drawing the sheet forwardly in the direction oftheir plain, the total travel provided being equal to two flankbreadths. This movement will have finally for its result to bring theflank in the making between the jaws 48 and 48' into the positionallotted to it underneath the last flank which has precedingly beenbrought in the same manner during the preceding cycle into the spacebetween the bars 49 and 49' between which it is now positioned.

To this end, the bars 49 and 49' rise and raise through the desredamount the fiank or sheet area held between them together with thefinished structure area 50 located above said bars.

During this double movement, the portion of a sheet comprised betweenthe undulating and broken lines limiting the edges of the clampin-gsystem 49, 49' and 48, 48' is stretched between the latter and executesin space a compound rotation the opposite Centers of which are notaligned since they lie 'actually along said edges which are broken orundulating.

When the flank which has just been formed reaches its final positionunderneath and preceding flank in the structure which is being formed,the section of a sheet which is not clamped between the bars and whichhas been turned around as disclosed while remaining connected with thebeginning of one fiank and the end of another, has entered the exactposition of the intermediate flan'k. It also assumes its final shape,since during the preceding movement, the molding of its surface has beengradually reversed by reason of its being constrained to match at eachmoment the changing Outline of its edges as produced through the gradualturning around of the latter.

At the end of the stroke considered, the clamping provided by the .fourjoining bars marks more deeply on the ridge lines and on the flanksbounded thereby the positions reached and the shapes;

The cycle continues thenafter so as to return the different parts intotheir starting positions. To this end and while the bars 49, 49' remainstationary and continue consequently holding the structure in position,the jaws or bars 48-48' are released and recede through a distance equalto twice the breadth or height of a flank. At this point, the jaws closeover the corrugated sheet which passes at S out of the forming means. Insaid position, it holds the sheet fast and consequently thereby theoperating structure. Its action allows thus the two bars 49 and 49' tobe released with reference to the two hollow sections in which they areengaged, said jaws or bars opening thus and Sinking by one step so as toengage the two following recesses which have just been formed in thesheet, this latter movement finishing one,- elementary cycle ofoperation.

The beginning of a further elementary cycle is begun by drawing outagain the sheet through the jaws 48 48', the successive cyclesprogressing all in the same manner as the first described cycle.

Turning to FIGS. 18, to 24, the latter illustrate different relativeOperating positions which may be given in turn to the four -bars of themachine of FIG. 16 and to the sheet and final structure 50 which latteris reduced for sake of simplification to a single line, during the mainsuccessive steps of a cycle of the type described hereinabove.

In FIG. 18, the bars or jaws 49, 49' of FIG. 16 are shown as holding thefinal structure 50 while the jaws 48, 48', are clamped over the originalsheet 45.

In FIG. 19, the jaws 48, 48' have progressed by more than one half oftheir total allowed stroke, and the jaws 49, 49' have risen by theoperative amount whereby the intermediate section of the sheet betweenthe two pairs of jaws -is modified and its shape is partly -impressed.

In FIG. 20, the jaws 48, 48' have reached the end of their stroke, thenewly formed fiank has taken its position and the shape of theintermediate sheet area has 17 been reversed and finally marked throughthe joining interengagement of the two bars or jaws.

In FIG. 21, the jaws 48, 48' have opened and then begun their returnstroke.

-In FIG. 22, the jaws 48, 48' have finished their return stroke and haveclosed over the corrugated sheet 45.

In FIG. 23, the two bars or jaws 49, 49' have moved apart.

In FIG. 24, they are now positioned to either side of a further flankincorporated into the chevron structure 50.

Turning back to FIG. 18, said jaws 49, 49' clamp between them the nextfiank in which a chevron folding is to be made. The cycle of operationmay now begin over agan.

The machine, the -kinematic operation of which has just been described,includes two main carriages as shown in FIG. 16: a carriage 51 whichcarries the bars 48 and 48' and which serves as a driving member drawingout the sheet 45 and a carriage 52 which moves with the bars 49 and 49'and holds in position the chevron structure 50. It includes furthermoreon each carriage two other mechanical members in the shape of jaws orslideways of a complementary type, the part played by which is to Shiftapart or to close respectively the bar 48 over the bar 48' and the bar49 over the bar 49'. FIG. 16 shows the auxiliary jaw 53' correspondingto the jaws 48' and the jaws 54, 54' corresponding to the jaws 49 and49', the jaw corresponding to the bar 48 being rigidly secured to thecarriage 51 and its Outline merging on the drawing with the outline ofthe jaw or bar 48'.

On one of 'the machines thus designed, these different movements areobtained by actuating the carriages through the agency of differentrollers running in Contacting relationship over four cams having asuitable Outline and mounted on a common central shaft executing onerevolution per cycle. In practice, however, these different movementsmay be executed in very different manners.

The machine thus constituted is suitable for producing structures theouter enclosing surfaces of which are plane and parallel, starting fromsheets of any desired substance which are to be folded in chevron shapeof a simple configuration, the flanks of the ridge lines beingconstituted by parallelograms or better still by corrugated surfaces. Asa matter of fact, such corrugated surfaces allow much more readi-ly areversal in the sh aping of the sheet then pleated or folded flanks,while producing however for an equal weight of material more' resistantstructures which are locked against deformation.

To the mechanical arrangements disclosed hereinabove should be addedcertain auxliaries when the structures to be produced have parallelridge lines which are not equidstant. In this case, the cams should forinstance have a thick frusto-conical periphery so that their stro'ke mayvary according as to whether the roller engaging them is in contact withthem. at one point or another of the cam generating line. Through thesemeans or any other equivalent means, the strokes executed for thedrawing of the sheet, the rotation of the intermediate area and for theraising of the structure may 'vary in length from one flank to theother, gradually or otherwise, provided that one or more guiding slopesof a suit-able shape ensure the lateral shifting of the rollers over thecams. It is thus possible to form structures having the shapeillustrated in FIG. 25 for instance.

:In addition to the different methods for producing chevron structuresaccording to the different methods as described hereinabove, I wish tomention also the possibility of employing conventional methods such ascold or hot stamping and swaging. These methods are applicable to thechevron folding of metals and substances which may be submitted to acertain elongation.

Thin metal sheets which are to be subjected to a deep stamping may as amatter of fact be stamped at room temperature over a certain eXtentbetween two suitably shaped dies of a press, provided however the anglesof the structures to be constructing are not too sharp. Lower grademetal sheets and thicker sheets may require an annealing or machining ata raised temperature.

Through stamping or swaging, it is possible to produce directly thechevrons on metals and substances liable to be worked without it beingpreviously necessary to shape them into sheets. The extent of thechevron shaping obtained at each compression step depends obviously onthe power of the machine.

A remarkable fact is that the sheets of material are submitted duringthe stamping of a chevron structure to an elongation which, although itis not identical at all points, provides however for the passage from adeveloped shape to a complex chevron configuration which remainsdevelopable. The structure obtained, when flattened out, produces asheet of a somewhat unequal thickness, which is larger than the originalshape both as to length and to breadth. The stamping betweenchevron-shaped dies may form thus a practical method for drawing out asheet through equally distributed local stresses.

All of the claims define a structure having ruled elementary surfaceswhich join each other along lines having points at which they changedirection and at each of which points border lines of at least four ofsaid elementary surfaces converge, the sum of the angles formed on saidsurfaces between said border lines at each of said points being equal to360. Due to the inherent limitations of manufacturing techniques,however, it is possible that the manufactured structure Will not complyabsolutely with the geometrical definitions in the claims.

For example, if the structures are made by means of a folding operationand a plurality of superposed sheets are folded at a given time, theridge lines of the protrusions of the outer sheet may not be as welldefined as those of the more centrally located sheets, viz, the walls ofthe protrusions in the former may be slightly rounded at their points ofmerger with other walls to a greater degree than those of the latter.

In view of this fact, the claims should be const-ued to cover suchslight departures from the absolute geometric configurations which aredefined.

When used in the specification and claims:

(1) the term ruled elementary surface" or "ruled surface" is to beconstrued to cover a geometrical figure which can be generated by astraight line. Cylinders, cones and hyperbolic paraboloids are examplesof such surfaces; and

(2) the term bends is to be construed to cover material which has beenshaped through a bending or folding operation, as distinguished from astamping or embossing operation or the like. In the latter cases, asdistinguished from the former, there is significant material flow,resulting in permanent deformation of the material.

It will be apparent to those skilled in the art that variousmodifications may be made in the steps of the methods which I havedescribed, and the apparatus for carrying out such methods, and thechevron products produced thereby, without going beyond the bounds of mydisclosure, and all such modifications which are within the scope of theappended claims I consider to be comprehended within the spirit of mydisclosure.

What I claim is:

1. A structural element comprisng a Sandwich of two cover sheets and aninterposed core sheet integrally secured with the cover sheets, saidcore sheet being corrugated with the corrugations extending in Zig-Zagparallel rows and each corrugation having a crest ridge Secured to onecover sheet and a Valley ridge secured to the other cover sheet, saidridges terminating in a peaked edge so that the core sheet can be formedby folding from a flat sheet without stretching the material, and saidcorrugations having inclined planar side walls between the crest andValley ridges.

2. A Sandwich type structural element comprising spaced opposed coversheets, a core sheet between said

1. A STRUCTURAL ELEMENT COMPRISING A SANDWICH OF TWO COVER SHEETS AND ANINTERPOSED CORE SHEET INTEGRALLY SECURED WITH THE COVER SHEETS, SAIDCORE SHEET BEING CORRUGATED WITH THE CORRUGATIONS EXTENDING IN ZIG-ZAGPARALLEL ROWS AND EACH CORRUGATION HAVING A CREST RIDGE SECURED TO ONECOVER SHEET AND A VALLEY RIDGE SECURED TO THE OTHER COVER SHEET, SAIDRIDGES TERMINATING IN A PEAKED EDGE SO THAT THE CORE SHEET CAN BE FORMEDBY FOLDING FROM A FLAT SHEET WITHOUT STRETCHING THE MATERIAL, AND SAIDCORRUGATIONS HAVING INCLINED PLANER SIDE WALLS BETWEEN THE CREST ANDVALLEY RIDGES.